In electronics, an integrated circuit (also known as an IC, chip, or microchip) is a miniaturized electronic circuit typically consisting of semiconductor devices and/or passive components. Integrated circuits are used in almost all electronic equipment in use today and have revolutionized the world of electronics. Computers, cellular phones, and other digital appliances are now inextricable parts of modern societies, made possible by the low cost of production of integrated circuits.
Due to the small feature sizes of semiconductor devices on ICs, it is critical to keep extremely tight tolerances during the fabrication process. For example, great lengths are taken to ensure that dielectric layers, such as gate oxides in transistors or dielectrics between plates of on-chip capacitors, have uniform thickness and conductivity. Defects and imperfections in these dielectric layers can result in a device not operating as planned over a predetermined operating range, or can even result in device failure. For example, weak spots, local contamination, unwanted residues, pre-damage by plasma enhanced processing steps, and so forth, can adversely affect a dielectric layer and ultimately reduce the life time of a device.
In an attempt to keep dielectric layers (and gate oxides in particular) uniform, high voltage tests are performed at various points in conventional fabrication processes. The goal of these tests is to identify any dielectric layer defects through abnormal device operation or device failure. If dielectric defects are found, engineers study the fabrication process to identify the underlying cause of the defect so it can be remedied as quickly as possible.
Unfortunately, however, until now direct physical failure analysis of a defective dielectric has been difficult, if not impossible, because conventional high voltage tests cause device failure by destroying the physical structure of the dielectric layer. For example, in many instances the high voltage tests cause thermal runaway of current over the device, which melts the dielectric and other nearby regions. Hence, physical analysis of the defective device and its dielectric (e.g. identifying chemical contaminants or the presence of micro cracks) has been difficult or impossible until now, because the original device structure is changed as a result of the catastrophic failure.